/Engine/Source/Runtime/Core/Public/Misc/PreloadableFile.h
Initialize theFPreloadableFileasynchronously, performing FileOpen operations on another thread. Use IsInitialized or WaitForInitialization to check progress.
void InitializeAsync ( [FCreateAsyncArchive](API\Runtime\Core\Misc\FPreloadableArchive\FCreateAsyncArchive) && InCreateAsyncArchiveFunction, uint32 InFlags, int64 PrimeSize )